Feat/painreportlist endpoint

[littlecoffe8]

Description

Add a new batch knowledge panel endpoint supporting one or multiple barcodes in a single request.

The new route:

GET /off/v1/knowledge-panel/?code=123,456

accepts comma-separated barcodes and returns a response indexed by barcode, with:

• panels for successful results
• errors for per-barcode failures

The existing single-product endpoint:

/off/v1/knowledge-panel/{barcode}

is preserved for backward compatibility.

The implementation follows the API format discussed in the October GitHub mobile/Dart discussion:

• singular /knowledge-panel/ route
• code query parameter
• comma-separated barcode format

lang handling is unchanged and still managed through the existing middleware.

country query parameters are currently ignored server-side (FastAPI ignores undeclared params), so there is no impact on the suffering calculation logic at the moment.

---

Code changes

• Added batch endpoint:

  GET /off/v1/knowledge-panel/?code=123,456
  

• Added parallel processing using asyncio

• Added batch response format:

  {
    "panels": {
      "123": {...}
    },
    "errors": {
      "456": {...}
    }
  }

• Preserved existing single-barcode endpoint

• Added unit tests covering:

  • single barcode batch requests
  • multiple barcode batch requests
  • partial failures
  • cache reuse behavior

• Refactored OFF HTTP calls to reuse a shared httpx.AsyncClient
  instead of creating a new client per request

• Added retry handling for transient OFF API failures (429, network issues, etc.)

---

How to test

You can test either through the OFF app or directly with curl.

Existing endpoint regression test

curl "http://127.0.0.1:8000/off/v1/knowledge-panel/3017620422003?lang=fr"

New batch endpoint with a single barcode

curl "http://127.0.0.1:8000/off/v1/knowledge-panel/?code=3017620422003&lang=fr"

New batch endpoint with multiple barcodes

curl "http://127.0.0.1:8000/off/v1/knowledge-panel/?code=3017620422003,3228857000166&lang=fr"

Batch endpoint with mixed success/failure cases

curl "http://127.0.0.1:8000/off/v1/knowledge-panel/?code=3017620422003,3450970045360&lang=fr"